The present invention relates to device and method for assessing drug levels within physiological fluids and, more particularly to apparatus and method for assessing lithium concentration within a patient's blood based on lithium concentration measured within the patient's saliva.
Lithium carbonate is a drug commonly used in the treatment of acute manias and depression syndromes. The therapeutic range of lithium in serum is about 0.4-1.2 meq/L. Serious lithium toxicity occurs at slightly higher serum levels (at least about 1.5 meq/L). The monitoring of lithium concentration within the blood is necessary for ensuring the safety of such treatment and to avoid toxicity. Thus, Lithium levels within the blood should be monitored frequently during the course of treatment, especially until a stable therapeutic level of lithium is reached.
Currently, the monitoring of lithium concentration within the blood involves a lengthy procedure which requires the employment of expensive equipment and professional operators for operating such equipment. A blood sample is extracted from the patient by a family doctor or a nurse. The extracted blood is collected within a sample tube. Following the addition of an anti-clotting material, the sample tube is transferred to a laboratory for analysis. At the laboratory, the plasma of the blood sample is separated from the blood cells by means of a centrifuge. The plasma is then transferred to another tube and is then analyzed by means of a flame photometer. The flame photometer is an expansive and cumbersome device which requires a professional operator. Further, the flame photometer is expensive to operate and has to be specifically prepared and calibrated prior to each examination. As a result, such device is usually activated only once or twice a week, after a substantial amount of blood samples have been collected. Following analysis of the blood sample, a written result is sent to the office and then to the family doctor. Such lengthy process (which may be extended for more than one week) may be ineffective in the sense that it does not provide an immediate feedback in the event of toxicity. Toxic levels of lithium within the patient's blood may occur as a result of introduction of over-dosage of the drug, or in the event of impaired clearance of the drug owing to damaged kidney or damaged liver. Lithium concentration within the blood is also dependent on hormonal regulation and other physiological factors and therefore may feature abnormal profile when the patient suffers from hormonal or other physiological problems. An immediate feedback is extremely important when treating children since relatively low concentrations of lithium may cause toxicity. Since there is no current effective treatment for lithium poisoning, an immediate feedback relating to lithium concentration within the blood is essential.
None of the prior art methods and devices provide substantially immediate feedback relating to lithium levels within the patient's blood and therefore such methods and devices are ineffective in detecting toxicity on time.
Further, none of the prior art methods and devices enables a doctor to independently conduct lithium concentration examinations without the need to use expensive and cumbersome equipment such as a flame photometer; without the need to send blood samples to laboratories equipped with such equipment; and without the need to employ professional operators for operating such equipment.
Further, none of the prior art methods and devices provides a non-invasive approach for monitoring lithium concentration within a patient's blood during a predetermined period of time.
There is thus a widely recognized need for, and it would be highly advantageous to have, method and device which provide substantially immediate feedback relating to lithium concentration within a patient's blood so as to effectively detect toxicity conditions on time.
It would be further advantageous to have such method and device which enable a doctor or a patient to independently conduct lithium concentration examinations without the need to use expensive and cumbersome equipment such as a flame photometer; without the need to end blood samples to laboratories equipped with such equipment; and without the need to employ professional operators for operating such equipment.
It would be further advantageous to have such method and device which enable to conduct such lithium concentration examinations non-invasively.